1. Technical Field
The present invention relates to a light source device and a projector, in particular to a technology of a light source device having a light emitting section partially covered by a secondary reflecting mirror.
2. Related Art
In the lamp used as a light source of a projector, specifically a discharge lamp such as a super-high pressure mercury lamp, there is used a reflector (a reflecting mirror) for reflecting light emitted from a light emitting tube. In the past, in order for obtaining bright images efficiently by a projector, there has been proposed a configuration of a light source device for improving efficiency of light emitted from a light emitting tube. For example, there has been proposed a technology of providing a secondary reflecting mirror covering a part of a light emitting tube separately from the reflector as a primary reflecting mirror (see e.g., Japanese Patent No. 3350003). The light reflected by the secondary reflecting mirror is input the primary reflecting mirror after passing through the light emitting tube, and then reflected frontward by the primary reflecting mirror. Thus, it becomes possible to make the light emitted from the light emitting tube efficiently proceed toward an optical system for using the light from the light source device, and at the same time, to achieve low-profiling of the light source device.
Since lamps used in projectors becomes in a high-temperature state on the ground that most of the electrical energy supplied thereto is turned into heat, it is often performed that air or the like is sprayed on light emitting tubes, thereby cooling the light emitting tubes. However, in the case of the configuration provided with the secondary reflecting mirror, in most cases there is insufficient space between the light emitting tube and the secondary reflecting mirror, insufficient air can only be sprayed to the portion covered by the secondary reflecting mirror, thus cooling might be insufficient.
In some cases, projectors are arranged to allow the user to use the projectors selectively in the upright state and in the inverted state, for example. If the use state of the projector is changed, the posture of the light source device is also changed, and the positional relationship between the light emitting tube and the secondary reflecting mirror is also changed in association therewith. In particular in the case in which the upper portion of the light emitting tube is covered by the secondary reflecting mirror, the heat becomes apt to be trapped between the light emitting tube and the secondary reflecting mirror, and accordingly, cooling is apt to be insufficient. In the portion of the light emitting tube, on which insufficient cooling is executed, there can arise the case in which a transparent member constituting the light emitting tube is crystallized with the heat to thereby become clouded.